BACKGROUND: Adapalene, a naftoic acid derivative with biological properties similar to those of the retinoic acid, is indicated in the treatment of acne vulgaris. OBJECTIVES: The present study was carried out to evaluate the therapeutic action of adapalene 0.1% gel and its tolerability in the treatment of mild to moderate acne vulgaris in patients living in Brazil. MATERIAL AND METHODS: Patients applied the gel at night for 12 weeks; and were evaluated regarding the efficacy and tolerability of the product according to the number of lesions observed at each of the 2-week and 12-week visits. RESULTS: Out of 125 patients, 81.6% completed 12 weeks of therapy and 10.4% of the cases left the study before week 12 because they were found to be lesion-free. Results allow us to confirm its effect upon keratinocyte cellular differentiation with antiinflammatory and antiproliferative properties. Adapalene induces a marked decrease in comedos and inflammatory lesions. Mild adverse events were reported in less than 10% of patients. CONCLUSION: Adapalene has been shown to be one of the best topical therapies for mild or moderate acne both in the present study and in previous studies.